1. Field of the Invention
This invention relates to a coupling device for connecting the power power take off means of an agricultural tractor to a driven shaft of an implement to be powered by the tractor power take off means. Such a coupling device includes an upper guide member pivotally mounted at its one end of the tractor and connectable at its other end to the implement either directly or through a coupling frame and, when a coupling frame is utilized the frame is conveniently further supported by a pair of lower guide members connected between the tractor and the frame. Such a coupling device further includes a drive shaft on the tractor connected to the power take off means thereof through a universal joint and being of a type which is automatically engageable with the driven shaft of the implement when the upper guide member and/or the coupling frame is connected to the implement.
2. Description of the Prior Art
Automatic drive shaft coupling devices per se are known and, for example, in GB-A-No. 2134217 there is disclosed a coupling device wherein both the drive shaft of the tractor and the driven shaft of the implement are suspended by resilient supports for alignment with one another during the coupling operation. However, after coupling has been effected, the drive shaft and the driven shaft remain in a resiliently supported condition. In operation, due to the relative articulation of the coupled drive shaft and driven shaft relative to the tractor and to the implement, unacceptably high resilient bias may continue to be applied to the shafts with consequential risk of overloading of the shaft and guard tube bearings.
A further type of coupling device is disclosed in DE-A-No. 2537841 in which the driven shaft on the implement is supported in the coupling position by a pivotal support. During the coupling operation such support is tilted by means of a lever which effectively shortens the length of the drive shaft train.